Is U.S. climate getting more extreme?

Is the climate in the U.S. getting more extreme? The answer to this question depends upon how one defines "extreme". For example, the number of extreme tornadoes (violent EF-4 and EF-5 twisters) has not increased in recent years. We lack the data to judge whether there has been an increase in severe thunderstorms and hail. There has been a marked increase in Atlantic hurricane activity since 1995 (though the possible contribution of human-caused global warming to this increase is not something hurricane scientists agree upon). Since it is difficult to quantify how severe storms like tornadoes and hurricanes are changing, a better measure of how climate extremes are changing is to look at temperature and precipitation, which are well-measured. NOAA's National Climatic Data Center (NCDC) has developed a Climate Extremes Index to attempt to quantify whether or not the U.S. climate is getting more extreme. The Climate Extremes Index (CEI) is based upon three parameters:1) Monthly maximum and minimum temperature2) Daily precipitation3) Monthly Palmer Drought Severity Index (PDSI)

The temperature data is taken from 1100 stations in the U.S. Historical Climatology Network (USHCN), a network of stations that have a long period of record, with little missing data. The temperature data is corrected for the Urban Heat Island effect, as well as for station and instrument changes. The precipitation data is taken from 1300 National Weather Service Cooperative stations. The Climate Extremes Index defines "much above normal" as the highest 10% of data, "much below normal" as the lowest 10%, and is the average of these five quantities:

1) The sum of (a) percentage of the United States with maximum temperatures much below normal and (b) percentage of the United States with maximum temperatures much above normal.

2) The sum of (a) percentage of the United States with minimum temperatures much below normal and (b) percentage of the United States with minimum temperatures much above normal.

3) The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

4) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

5) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.

Figure 1. The Annual Climate Extremes Index (CEI), updated through 2008, shows that U.S. climate has been getting more extreme since the early 1970s. Image credit: National Climatic Data Center. On average since 1910, 20% of the U.S. has seen extreme conditions in a given year (thick black line).

As summarized by Gleason et al. (2008), the National Climatic Data Center concludes that based on the Climate Extremes Index, the percentage of the U.S. seeing extreme temperatures and precipitation generally increased since the early 1970s. These increases were most pronounced in the summer. No trend in extremes were noted for winter. The annual CEI index plot averaged for all five temperature and precipitation indices (Figure 1) showed that five of the fifteen most extreme years on record occurred since 1997. Shorter-lived periods with high CEI values occurred in the 1930s and 1950s, in association with widespread extreme drought and above-average temperatures. The most extreme year in U.S. history was 1998, with 1934 a close second. The year 1998 was the hottest year in U.S. history, with a record 78% of the U.S. experiencing minimum temperatures much above normal. That year also had a record 23% of the U.S. with much greater than normal precipitation from extreme 1-day precipitation events. The 1934 extreme in CEI was due in large part because of the most widespread drought of the century--a full 52% of the U.S. was affected by severe or extreme drought conditions. That year also saw a record 64% of the U.S. with much above normal maximum temperatures.

The impact of maximum and minimum temperatures on the Climate Extreme IndexIt is very interesting to look at the five separate indices that go into the Climate Extremes Index. Today I'll look at temperature, and next week, I'll focus on drought and precipitation. The portion of the U.S. experiencing month-long maximum temperatures either much above normal or much below normal has been about 10% over the past century (black lines in Figure 2). However, over the past decade, about 20-25% of the U.S. has been experiencing monthly maximum temperatures much above normal, and the portion of the U.S. experiencing much colder than normal high temperatures has been near zero. Minimum temperatures show a similar behavior, but have increased more than the maximums (Figure 3). Over the past decade, minimum temperatures much above normal have affected 25-35% of the U.S. This means that the daily range of temperature (difference between minimum and maximum) has decreased over the past decade, which is what global warming says should be happening if greenhouse gases are primarily to blame for the rise in temperatures.

While there have been a few years (1921, 1934) when the portion of the U.S. experiencing much above normal maximum temperatures was greater than anything observed in the past decade, the sustained lack of maximum temperatures much below normal over the past decade is unique. The behavior of minimum temperatures over the past decade is clearly unprecedented--both in the lack of minimum temperatures much below normal, and in the abnormal portion of the U.S. with much above normal minimum temperatures. Remember that these data ARE corrected for the Urban Heat Island effect, so we cannot blame increased urbanization on the increase in temperatures. Recall that the all-time record maximum and minimum temperature data, which I presented in a post in February, are not corrected for the Urban Heat Island Effect, but look very similar to the CEI maximum and minimum temperature trends presented here.

A lot of people have told me that they believe we are experiencing more wild swings of temperature from hot to cold from day to day in recent years, but the CEI data does not answer this question. To my knowledge, a study of this kind has not been done.

Figure 2. The Annual Climate Extremes Index (CEI) for maximum temperature, updated through 2008, shows that 20-25% of U.S. has had maximum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.

Figure 3. The Annual Climate Extremes Index (CEI) for minimum temperature, updated through 2008, shows that 25-35% of U.S. has had minimum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.

Annual WeatherDance contest ready for registration!Armchair forecasters, now's your chance to shine! WeatherDance, based on teams in the men's and women's NCAA basketball tournaments, allows players to predict which team's city will be hotter or colder on game day in each round of the Big Dance. Beginning today, players can make their forecasts at the Weather Dance Web site at: www.weatherdance.org. The site will be updated with cities promptly after NCAA seeding announcements. First round Weather Dance selections must be entered by 11:59 p.m. EDT Wednesday, March 18.

"Officially, Weather Dance began as a class project to get students involved in weather forecasting, but we kept it around because it got popular. People think they can do better forecasting than the meteorologists. Well, here's their shot!" said Perry Samson, WeatherDance creator, co-founder of the The Weather Underground, Inc., and Professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan.

This is the fifth year for the game. Last year more than 2,000 people played. Most play merely for the thrill, but many K-12 science teachers involve their classes as part of meteorology units. The winning teacher will receive an expense-paid trip to join the Texas Tech/University of Michigan Storm Chasing team this spring for a day of tornado chasing in Tornado Alley. Other winners will receive a Weather Underground umbrella, "Extreme Weather" mugs, or a copy of the book "Extreme Weather," by Christopher C. Burt.

I'll talk about drought and precipitation trends in my next post, Monday or Tuesday.

ok vortix, i watched part of his online show. i do have a question to ask conservatives though. he posted a listing of his principles.heres one i found interesting.

#8. It is not un-American for me to disagree or share my personal opinion.

but yet, why didnt that principle apply to liberals who protested the iraq war? they were certainly called 'unamerican' by conservatives, and only for expressing their opinions. i guess #8 only applies now that theres a democratic majority in congress and in the white house.

sorry for the rather non weather topic. on a weather note, swfla weather has been great the last few days!

Can someone show me where the UHI adjustment is made in the CEI? Maybe I missed it, but I didn't see it in the article linked. The temp pictures have the NOAA emblem, and I thought they didn't make any UHI adjustments. I know GISS makes an UHI adjustment, but I don't believe that data is being used here. Thanks

Quoting barryweather:People, people. I feel left out. I've been waitning for heated discussion like this for weeks, but I've bee to busy to get into it and know I have to go home.

"let let the minority take control of your world and toss logic and rational out the window"

Dude, I really hope you didn't mean this the way it sounded.

One more point...one day my generation and my children and grandchildren certainly will have to accept life with less fossil fuel or none because it will run out if used at the current pace. Perhaps with the exception of coal oil and natural gas will become less abundant and the "majority" (that includes all races) of people on this Earth will not be able to afford it.

There are ways that we can work to make it last longer and most of the posters here seem to be against it.

People, people. I feel left out. I've been waitning for heated discussion like this for weeks, but I've bee to busy to get into it and know I have to go home.

"let let the minority take control of your world and toss logic and rational out the window"

Dude, I really hope you didn't mean this the way it sounded.

One more point...one day my generation and my children and grandchildren certainly will have to accept life with less fossil fuel or none because it will run out if used at the current pace. Perhaps with the exception of coal oil and natural gas will become less abundant and the "majority" (that includes all races) of people on this Earth will not be able to afford it.

There are ways that we can work to make it last longer and most of the posters here seem to be against it.

. CycloneOz 9:23 PM GMT on March 13, 2009 Quoting floridafisherman:...feces...care to place some into a cup of water and drink it.

...and only an american liberal would suggest something as vile, disgusting, and perverted as that. -------

but wait a minute ozzy! YOU were the one who said "feces is not a pollutant". so please, back up your statement. prove that it is not. i mean, if feces are so wonderful (and since yours smell so nice and fresh), why not?

could it be because you really dont know '$hit'?

as for your liberal comment, it only goes to prove my theory that conservatives are the lowest of the low. and im not a liberal btw lol, which makes your answer seem even more foolish.

Oh my. Looks like every living thing on the planet has to leave for they are polluting by virtue of their droppings. No more fertilizer. Look, you all can argue until the Sun explodes, which will ultimately happen. Excepting that your life revolves around the use of carbon producing stored energy is not a choice. Its the fact. You will probably never see the day that the alternatives can replace what is in place. Do some math.

Strive to find viable alternatives without starving the poor or pushing the cost of foods and or essentials beyond reach. Lets start by taking everyones PC and video games away. Then their phones and cars and medical care, and your freedom of choice. Then lets take a poll and see who is crying foul.

If you don't give someone the power to bother you, then they can't. Liberal or conservative, we are where we are in time. How we move forward is a choice that will be made for you if you let the minority take control of your world and toss logic and rational out the window.

This is a pretty rude post. One could say I was rather distracted after the first sentence.

Despite your attempt at posting in a public forum, your attempt at successful communication has failed.

Yes, please post whatever you want for everyone else to see-------------well, you did reply, so apparently my attempt was successful and not failed.

also, when the subject came up on air pollutants and health risks, YOU were the one who deflected the question directed at you and told the other guy to "look up life expectantcy". looking at the average LE wont tell you if those ppl had health issues or not. i mean, people that live near chernobyl could easily have the same LE of ppl in toronto, but that doesnt mean the chernobyl people are any healthier than the toronto ppl.

Report from Rice U on lessons learned, but not applied during evac for Ike.

"The timing of evacuations showed no improvement over the experience during Hurricane Rita, when roadways experienced paralyzing gridlock," Stein said. "People evacuating from hurricane Ike all left too late, potentially creating the same conditions that existed during Hurricane Rita had a larger population evacuated."

Quoting floridafisherman:Care to look up the life expectancy in the US since we started burning fossil fuels? The answer does not fit your mold.

thats a pretty stupid assumption. we have higher life expectancys because of better medical care. and yes, things like smoke, smog, and other pollutant CAN KILL! apparrently, despite your attempt at intellect, you have overlooked simple weather and health facts. anything besides air that enters your lungs is a contaminate.

do you need to be provided a link describing the health side effects of smog, smoke, and other pollutants?

This is a pretty rude post. One could say I was rather distracted after the first sentence.

Despite your attempt at posting in a public forum, your attempt at successful communication has failed.

Yes, please post whatever you want for everyone else to see.

And you clearly don't think that being able to see textbooks or wounds on the operating table after dark has anything at all to do with it. How do you like all of those organic, naturally occurring, self-powering devices in your average hospital room or doctor's office?

Care to look up the life expectancy in the US since we started burning fossil fuels? The answer does not fit your mold.

thats a pretty stupid assumption. we have higher life expectancys because of better medical care. and yes, things like smoke, smog, and other pollutant CAN KILL! apparrently, despite your attempt at intellect, you have overlooked simple weather and health facts. anything besides air that enters your lungs is a contaminate.

do you need to be provided a link describing the health side effects of smog, smoke, and other pollutants?

too much Vit C can poison youAnd water to a newborn is deadly as are a number of native plants growing in my yard.

These include human health problems caused by air pollution from the burning of coal and oil & by studies it is a huge unexceptable amount of health costS & sickness~ damage to land from coal mining and to miners from black lung disease, flattened mountains, environmental degradation caused by global warming, acid rain, oil spills and water pollution, ocean acidification

Care to look up the life expectancy in the US since we started burning fossil fuels? The answer does not fit your mold.What argument do you have we shouldn't start making our best atempts at switching to clean energy? If we could get some companies making panels, they would be cheaper.. I could plug my car into them to charge, Get a check from the power company for the energy I sold them.. instead of them adding a bunch of new coal plants & CHARGING US MORE. Those monthly checks would help stimulate the economy...Kind of like what Germany has done.

When this actually cost-effective, far more reliable, and doesn't require huge sums of upfront energy and funding it will happen all by itself. I only plan on paying for it with my taxes if I get a panel for free and I only pay for one with my taxes...not anyone else's.

Very true, but if I am in the forest and smell smoke, I am not going to do a transect of the entire forest to check for areas of fire. I am damn well going to assume there could be a fire and act accordingly.

But don't you think that everyone would appreciate you finding out if it is a campfire before you call in the air tankers?

My point was that it is certainly not a "naturally occuring" element and it is purely a by-product of atomic energy in the age of man......We dodged the radioactive menace, for now, with the end of the Cold War but nature does have a hard time overcomng extensive radiation...Might not destroy the earth but it certainly puts a damper on "local" areas subjected to ground level atomic testing or the occassional nuclear meltdown like Chernobol........

Oz~ too much Vit C can poison you. This goes so far beyond CO2. Burning oil, coal, gas & corn have costs that are not included in consumer utility or gas bills, nor are they paid for by the companies that produce or sell the energy. These include human health problems caused by air pollution from the burning of coal and oil & by studies it is a huge unexceptable amount of health costS & sickness~ damage to land from coal mining and to miners from black lung disease, flattened mountains, environmental degradation caused by global warming, acid rain, oil spills and water pollution, ocean acidification~ there is national security costs, such as protecting foreign sources of oil. Even if you don't believe burning this stuff doesn't cause some of these~ enough of these are undisputed & worthy causes to quit the habit. We are using more than we thought we would & it's only gonna get worse. What argument do you have we shouldn't start making our best atempts at switching to clean energy? If we could get some companies making panels, they would be cheaper.. I could plug my car into them to charge, Get a check from the power company for the energy I sold them.. instead of them adding a bunch of new coal plants & CHARGING US MORE. Those monthly checks would help stimulate the economy...Kind of like what Germany has done.

Afternoon Folks from the Florida Big Bend...."April Showers.........[err March] bring May Flowers"......Hope we get some of that rain over TX/LA over here in Northern Florida over the weekend.....Pollen levels are very high over here (causing a lit of folks like my Wife some major nasal/headache discomfort)and we need some rain to slow down th pollen release from all the Oak trees down a little bit......

Tornadoes might not be increasing in the USA, but they're likely to increase in both intensity and frequency in Canada as the "Tornado Alley" pushes northeast. It's going to be sunny and warm the next few days in S. Ontario.

Quoting CycloneOz:CO2 is not a pollutant. Calling it a pollutant is offensive to me since I exhale CO2 as a natural function of my respiration.

You also excrete feces. However, you are not allowed to dump it anywhere you like (assuming you are living in the US and following the laws of your state and the regulations of your county and/or municipality.)

And that is true of your "grey water" (from your sink) too. In most locals it must be sent down the sewer.

Your society around you requires of you to cooperate for the greater good.

That you also exhale CO2 is of no relevance to AGW as animal respiration is normally offset with plant growth. That indeed is the grand bargain of evolution on planet Earth - the CO2 exhaling species are symbionts of the O2 producers. What man has done through the industrial revolution is create a CO2 production capability beyond the ability of the O2 producers to exploit in any time frame relevant to a human lifetime.

Volcanoes are known to spew out much more of that CO2 human emission. Could this be the reason why the Arctic saw a record minimum?

Volcanoes under the Arctic sea was discussed extensively in 2008... Much to the chagrin of the denial-sphere, not much hay could be made from them. The amount of energy brought into the waters of the Arctic by volcanoes, from within the mantle, is small compared to the radiation from the sun.

Atmoaggie, California actually has not been showing very strong signs of global warming. In fact, parts of coastal California got colder while the rest of the US largely got warmer. This may be due to the land warming in the desert, while the ocean stays colder, which drives an increase in fog and marine layer clouds, which in turn make summer temperatures much cooler in some areas. Also, California's climate is extremely variable, and California is actually in a relatively wet period right now, so a 'drought' like the one we are having now is pretty normal.

Also:

It is hard to gauge the size of a forest if you are looking at only a few trees in the middle of it, eh?

:)

Very true, but if I am in the forest and smell smoke, I am not going to do a transect of the entire forest to check for areas of fire. I am damn well going to assume there could be a fire and act accordingly.